SELECT sno FROM sc WHERE cno="c1"AND cno="c2" SELECT sno FROM sc WHERE cno="cl',AND SELECT sno FROM sc WHERE cno="c2" SELECT sno FROM sc WHERE cno="cl" UNION SELECT sno FROM sc WHER:E cno="c2" SELECT sno FROM sc WHERE cno="cl"AND sno IN(SELECT sno FROM sc WHERE cno="c2")